Displays and capture devices come in many different form factors. A display can be a television, a monitor, a cinema screen, a projector screen, etc. A capture device can be an image sensor in an imaging device, such as a still camera and video camera. The image sensor may be any device that converts an optical image to an electrical signal, e.g., a charge-coupled device (CCD) and a complementary metal-oxide-semiconductor (CMOS) active-pixel sensor. The area on the display or the surface of the capture device may also be called a “screen,” and is usually rectangular in shape. For these rectangular screens, the shape of the screen is quantitatively described by its “aspect ratio.” An aspect ratio is the ratio of the length of the longer side of the screen to the length of the shorter side of the screen. Common video aspect ratios include 1.33, 1.77, 1.85, and 2.35. Sometimes, however, the screen captures or displays a signal that is of a different aspect ratio. For example, a widescreen movie may be projected onto a standard television set.
A common solution to this mismatch problem is called “letterboxing.” The idea is to scale the rectangular signal to fit either the width or the height of the screen. Any spare height or width in the screen is left blank. For example when letterboxing the widescreen movie onto the standard television set, one can see black bands above and below the movie. This solution leaves parts of the screen unused, and the size of the projected or captured signal is unnecessarily diminished.
Another aspect ratio problem relates to the need for photographers and videographers to capture images at different aspect ratios. Currently, for example, a photographer must generally use a separate camera for each aspect ratio, e.g., 3:2 for a standard digital camera, 4:3 for a traditional camera and 4:5 for a large-format camera.
What is needed are techniques that maximize the usable screen area while accommodating signals of different aspect ratios.